Bottom Line:
Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet.We identified an immunodominant peptide recognized by the majority of individual patients'sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis.Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.

Affiliation: Department of Medicine, Section of Internal Medicine, University of Verona, Verona, Italy.

ABSTRACTType 1 diabetes is characterized by autoimmune destruction of pancreatic beta cells. The role played by autoantibodies directed against beta cells antigens in the pathogenesis of the disease is still unclear. Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet. To clarify these issues, we screened a random peptide library with sera obtained from 58 patients with recent onset type 1 diabetes, before insulin therapy. We identified an immunodominant peptide recognized by the majority of individual patients'sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis. Antibodies against the peptide affinity-purified from patients' sera, recognized the viral protein and autoantigens; moreover, such antibodies induced apoptosis of the beta cells upon binding the L-type calcium channels expressed on the beta cell surface, suggesting a calcium dependent mechanism. Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.

Mentions:
To better characterize the interaction between our antibodies and CACNA1D we synthetised a seven aa peptide (GNLEHVS, called CA peptide) derived from CACNA1D and sharing homology with the T1DM peptide. We firstly verified that the peptide was recognized by antibodies purified against the T1DM peptide, the COXSA and the CA peptides in ELISA (Fig. 4A). Secondly we tested whether the peptide was recognized by the sera of patients with type I diabetes. Sixty-one out of 80 (76%) patients’sera had IgG antibodies against the CA peptide in ELISA, whereas none of the 50 controls’sera bound the peptide (Fig. 4B). These results indicate that anti-peptide antibodies react with particular type of VGCC, CACNA1D and suggest that CACNA1D may represent an important and yet unidentified autoantigen target in type I diabetes.

Mentions:
To better characterize the interaction between our antibodies and CACNA1D we synthetised a seven aa peptide (GNLEHVS, called CA peptide) derived from CACNA1D and sharing homology with the T1DM peptide. We firstly verified that the peptide was recognized by antibodies purified against the T1DM peptide, the COXSA and the CA peptides in ELISA (Fig. 4A). Secondly we tested whether the peptide was recognized by the sera of patients with type I diabetes. Sixty-one out of 80 (76%) patients’sera had IgG antibodies against the CA peptide in ELISA, whereas none of the 50 controls’sera bound the peptide (Fig. 4B). These results indicate that anti-peptide antibodies react with particular type of VGCC, CACNA1D and suggest that CACNA1D may represent an important and yet unidentified autoantigen target in type I diabetes.

Bottom Line:
Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet.We identified an immunodominant peptide recognized by the majority of individual patients'sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis.Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.

Affiliation:
Department of Medicine, Section of Internal Medicine, University of Verona, Verona, Italy.

ABSTRACTType 1 diabetes is characterized by autoimmune destruction of pancreatic beta cells. The role played by autoantibodies directed against beta cells antigens in the pathogenesis of the disease is still unclear. Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet. To clarify these issues, we screened a random peptide library with sera obtained from 58 patients with recent onset type 1 diabetes, before insulin therapy. We identified an immunodominant peptide recognized by the majority of individual patients'sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis. Antibodies against the peptide affinity-purified from patients' sera, recognized the viral protein and autoantigens; moreover, such antibodies induced apoptosis of the beta cells upon binding the L-type calcium channels expressed on the beta cell surface, suggesting a calcium dependent mechanism. Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.